/*
 * Copyright 2002-2021 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hqd.ch03.v51.core.type.classreading;

import com.hqd.ch03.utils.ClassUtils;
import com.hqd.ch03.v51.core.annotation.AnnotationFilter;
import com.hqd.ch03.v51.core.annotation.MergedAnnotation;
import com.hqd.ch03.v51.core.asm.AnnotationVisitor;
import com.hqd.ch03.v51.core.asm.SpringAsmInfo;
import com.hqd.ch03.v51.core.asm.Type;

import java.lang.annotation.Annotation;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Consumer;

/**
 * {@link AnnotationVisitor} that can be used to construct a
 * {@link MergedAnnotation}.
 *
 * @param <A> the annotation type
 * @author Phillip Webb
 * @since 5.2
 */
public class MergedAnnotationReadingVisitor<A extends Annotation> extends AnnotationVisitor {


    private final ClassLoader classLoader;


    private final Object source;

    private final Class<A> annotationType;

    private final Consumer<MergedAnnotation<A>> consumer;

    private final Map<String, Object> attributes = new LinkedHashMap<>(4);


    public MergedAnnotationReadingVisitor(ClassLoader classLoader, Object source,
                                          Class<A> annotationType, Consumer<MergedAnnotation<A>> consumer) {

        super(SpringAsmInfo.ASM_VERSION);
        this.classLoader = classLoader;
        this.source = source;
        this.annotationType = annotationType;
        this.consumer = consumer;
    }

    @SuppressWarnings("unchecked")
    public static <A extends Annotation> AnnotationVisitor get(ClassLoader classLoader,
                                                               Object source, String descriptor, boolean visible,
                                                               Consumer<MergedAnnotation<A>> consumer) {

        if (!visible) {
            return null;
        }

        String typeName = Type.getType(descriptor).getClassName();
        if (AnnotationFilter.PLAIN.matches(typeName)) {
            return null;
        }

        try {
            Class<A> annotationType = (Class<A>) ClassUtils.forName(typeName, classLoader);
            return new MergedAnnotationReadingVisitor<>(classLoader, source, annotationType, consumer);
        } catch (ClassNotFoundException | LinkageError ex) {
            return null;
        }
    }

    @Override
    public void visit(String name, Object value) {
        if (value instanceof Type) {
            value = ((Type) value).getClassName();
        }
        this.attributes.put(name, value);
    }

    @Override
    public void visitEnum(String name, String descriptor, String value) {
        visitEnum(descriptor, value, enumValue -> this.attributes.put(name, enumValue));
    }

    @Override

    public AnnotationVisitor visitAnnotation(String name, String descriptor) {
        return visitAnnotation(descriptor, annotation -> this.attributes.put(name, annotation));
    }

    @Override
    public AnnotationVisitor visitArray(String name) {
        return new ArrayVisitor(value -> this.attributes.put(name, value));
    }

    @Override
    public void visitEnd() {
        MergedAnnotation<A> annotation = MergedAnnotation.of(
                this.classLoader, this.source, this.annotationType, this.attributes);
        this.consumer.accept(annotation);
    }

    @SuppressWarnings("unchecked")
    public <E extends Enum<E>> void visitEnum(String descriptor, String value, Consumer<E> consumer) {
        String className = Type.getType(descriptor).getClassName();
        Class<E> type = (Class<E>) ClassUtils.resolveClassName(className, this.classLoader);
        consumer.accept(Enum.valueOf(type, value));
    }

    @SuppressWarnings("unchecked")

    private <T extends Annotation> AnnotationVisitor visitAnnotation(
            String descriptor, Consumer<MergedAnnotation<T>> consumer) {

        String className = Type.getType(descriptor).getClassName();
        if (AnnotationFilter.PLAIN.matches(className)) {
            return null;
        }
        Class<T> type = (Class<T>) ClassUtils.resolveClassName(className, this.classLoader);
        return new MergedAnnotationReadingVisitor<>(this.classLoader, this.source, type, consumer);
    }

    /**
     * {@link AnnotationVisitor} to deal with array attributes.
     */
    private class ArrayVisitor extends AnnotationVisitor {

        private final List<Object> elements = new ArrayList<>();

        private final Consumer<Object[]> consumer;

        ArrayVisitor(Consumer<Object[]> consumer) {
            super(SpringAsmInfo.ASM_VERSION);
            this.consumer = consumer;
        }

        @Override
        public void visit(String name, Object value) {
            if (value instanceof Type) {
                value = ((Type) value).getClassName();
            }
            this.elements.add(value);
        }

        @Override
        public void visitEnum(String name, String descriptor, String value) {
            MergedAnnotationReadingVisitor.this.visitEnum(descriptor, value, this.elements::add);
        }

        @Override

        public AnnotationVisitor visitAnnotation(String name, String descriptor) {
            return MergedAnnotationReadingVisitor.this.visitAnnotation(descriptor, this.elements::add);
        }

        @Override
        public void visitEnd() {
            Class<?> componentType = getComponentType();
            Object[] array = (Object[]) Array.newInstance(componentType, this.elements.size());
            this.consumer.accept(this.elements.toArray(array));
        }

        private Class<?> getComponentType() {
            if (this.elements.isEmpty()) {
                return Object.class;
            }
            Object firstElement = this.elements.get(0);
            if (firstElement instanceof Enum) {
                return ((Enum<?>) firstElement).getDeclaringClass();
            }
            return firstElement.getClass();
        }
    }

}
